Author Bio

Dr. Dietz has over 43 years of experience in the Chemical and Electronic Industries. During his 43 years with DuPont he held a variety of managerial positions in the fields of dyestuff, pigment, and electronic materials technologies, in support of product and process development, application studies, technical customer support, training, and manufacturing technical support. Dr. Dietz is a well known expert in the area of material and process technology for printed circuit boards and substrates. He is the author of the book Dry Film Photoresist Processing Technology and he has published extensively on printed circuit board fabrication technology. He was Technical Editor of CircuiTree Magazine where he published monthly. In 2000, Dr. Dietz was named by PC FAB Magazine and ATOMIC 29 as one of the 50 most influential people in the PCB industry. In 2001 he earned DuPont Electronics' prestigious Winning Spirit award. In 2009 he received the Best Technical Paper award at the Electronic Circuits World Convention in Shanghai, China. He has been active in the PCMI (Photochemical Machining Institute) and the IPC and has contributed to the IPC National Technology Roadmap for Electronic Interconnections as well as the iNEMI Technology Roadmap. He was DuPont's representative at ITRI (Interconnect Technology Research Institute). Recently he founded Karl Dietz Consulting LLC. Dr. Dietz holds a PhD in Organic Chemistry from Frankfurt University, Germany.

Karl's Tech Talk: Digital Imaging Update

Through the years, I have repeatedly covered and updated digital imaging in this column, from as far back as 1997 in CircuiTree, through a column in this magazine in November 2015. Several reasons for this extended coverage include the fact that technology had a slow, long incubation time that eventually led to accelerated improvements and acceptance for mass production. It might also be argued that, next to the development of microvia technologies, digital imaging is probably the most innovative technology to achieve high-density interconnects in acceptable yields.

It is worth mentioning that digital imaging is a more appropriate term to refer to this technology than laser direct imaging (LDI) because LDI is just one example of digital imaging, albeit its pioneering version.

The advantages of digital circuitization techniques have been described in detail by suppliers of equipment and photoresist. Since phototool generation and conditioning are omitted, there is the advantage of shorter lead time. Small lots can be customized at no extra cost (e.g., with added date and lot number information). Maybe the biggest advantage is the ability to scale (i.e., to change the dimension of each individual exposure for best fit to reference points on an underlying pattern of a multilayer structure). However, early digital imaging systems had substantial drawbacks, such as Orbotech’s DP100 which used an argon ion laser with limited radiation power, high power usage, and high cooling requirements.

For years, laser direct imaging (LDI) was synonymous with digital imaging. While most early, commercially successful digital processes involved the use of lasers, other more recent processes use non-laser light sources such as LEDs (light emitting diodes) that consume less power, last longer, and have higher light intensity output. Alternatively, various types of mercury lamps are employed, with more than one wavelength used for imaging. Others use inkjet technology to build digitally imaged patterns such as legend print, soldermask or etch resist.

2016

Through the years, I have repeatedly covered and updated digital imaging in this column, from as far back as 1997 in CircuiTree, through a column in this magazine in November 2015. Several reasons for this extended coverage include the fact that technology had a slow, long incubation time that eventually led to accelerated improvements and acceptance for mass production.

Electronic packaging refers to the integration of electronic elements into a functioning device by forming connectivity at different levels. One distinguishes between different levels of electronic packaging, a convention that is not always consistent.

In general, “green” and “environmentally friendly” refer to manufacturing that involves the replacement of toxic substances with less toxic materials, the elimination of materials or processing steps, less consumption of chemicals (i.e., more efficient or higher yield processing), reduction of water use, reduction of energy use, less space requirement (i.e., smaller equipment footprint), recycling, and on-site recovery of materials.

2015

The advantages of digital circuitization techniques have been described in detail by suppliers of equipment and photoresist. Since phototool generation and conditioning are omitted, there is the advantage of shorter lead time.

Dry film photoresist suppliers typically indicate for which process a certain resist type is suitable; however the fabricator still has to select the resist thickness that matches his needs best. The most important thickness selection criteria that come to mind are price, resolution, and yield.

In this article, Karl Dietz talks about the qualities of quick-turn circuit board shops and their processing techniques and technologies. He also highlights some of the technologies that enable fast delivery for these quick-turn board shops, and how they are also suitable for mass production.

Lucent looked at the development of optical backplanes in the early 2000s, but financial problems interfered. But there remained continued interest and work on optical backplanes. In this column, Karl Dietz talks about the technical issues in integrating optoelectronics in backplanes, and the continued work in the segment.

Radiative loss is only a small component of loss contributors. Coupling to adjacent lines, on the other hand, can cause signal rise time degradation. It can be modeled quite accurately and proper circuit layout can minimize it.

2014

Laminate construction, chemical composition of the copper foil surface and its topography, resist composition, lamination conditions, and hold times all affect dry film photoresist adhesion, conformation, and, ultimately PWB yields. As Karl Dietz explains, a number of resist adhesion test methods have been employed to test different surfaces and process conditions with regard to dry film adhesion.

Higher lamination pressure results in improved dry film resist conformation to the board surface. However, there are practical limitations to increasing the lamination pressure due to the design of a particular model of automatic cut sheet laminator. Even if a high-pressure setting is compatible with the design of the laminator, it may be difficult to take advantage of the higher pressure.

In the world of PCB fabrication, there are few examples of special support features for thin substrates. But they do exist in the form of assist features in conveyorized spray modules designed to prevent mishaps during the transfer of very thin innerlayers, or in the transport of flex circuit boards, employing the use of leaders or frames.

Karl Dietz writes, "'Green' and 'environmentally friendly' are ill-defined terms. In general, these terms refer to manufacturing that involves the replacement of toxic substances with less toxic materials, the elimination of materials or processing steps, and less consumption of chemicals..."

Columnist Karl Dietz writes, "Silver halide films are much more versatile than diazo films and can be used in a broader range of applications than the diazo materials. High-speed films are typically 100,000 times faster than diazo films, allowing them to be used in low light and high-speed recording applications such as photo plotters, cameras, and step-and-repeat machines."

Columnist Karl Dietz writes, "Phototools are either silver or diazo. The objective of this column is to familiarize you with diazo phototools. Less common, and more expensive, are chrome-on-glass phototools. Diazo phototools are transparent even in the darker, unexposed areas and they come with a characteristic amber color."

2013

The objective of this column from Karl Dietz is to familiarize you with artwork generation, the film types, and properties of silver and diazo films. Some technologies, no longer practiced, are mentioned to illustrate innovation and change over several decades.

Miniaturization of electronic devices has been a trend over decades and is continuing into the foreseeable future. How this trend affects the reliability of these devices is an important question. Some processes, when applied to ever-smaller dimensions, reach a point where they yield less reliable structures, and changes in materials and processing are necessary to maintain reliability.

Environmental and cost issues have slowly encouraged the transition away from solvents, especially halogenated hydrocarbons, toward the use of aqueous chemistries and water-miscible solvents. This has paved the way for the development of new photoresists and fluxes.

Laser ablation approaches differ by laser source and in the type of material being ablated. Ablation of dielectric, metal, or resist are examples of techniques that differ in the material being ablated. Karl Dietz presents laser applications for patterning in PCB fabrication and reviews a number of other applications.

Screen printing applications for fabrication and assembly of PCBs and electronic packages and devices vary, depending on use. In the second half of his two-part column Karl Dietz reviews the choices available to the industry.

2012

In this series, Tech Talk captures the variety of non-conventional circuitizing technologies, including those that have matured into mass production, some that are still in development, and those abandoned or dormant. Many of the processes involve the use of lasers, while some techniques use non-laser light sources.

This new series captures the variety of non-conventional circuitizing technologies, including those that have matured into mass production, some that are still in development, and those abandoned or dormant. Many of the processes involve the use of lasers, while some techniques use non-laser light sources.

One goal of copper surface preparation is to create a copper topography that allows maximum contact between the copper and the dry film resist, which is a prerequisite for film adhesion to copper. The copper topography has to match the film rheology and its ability to flow under lamination conditions.

Continuing on from last month’s Tech Talk column (Advances in Copper Plating, Part A), this second column in a two-part series on copper plating for electronic applications examines conveyorized plating modules and pulse plating.

Before entering the world of electronics, where I was surprised and puzzled by the presence and role of colorants in photopolymer formulations, it was my privilege to have worked in the field of dyestuffs and colored pigment research. Color in photoresists has been addressed in this column before, but it's time for a renewed discussion.

From global PCB production statistics to leading technology and process advances, industry veteran Karl Dietz crunches the numbers and provides his unique perspective of the events and trends in the PCB industry in 2011.

2011

Random defects, "repeat" defects and even "pseudo repeat defects" may affect several panels, or plague an entire production run in printed wiring board fabrication. Before you can do something about them, the key is locating and identifying them.